The probabilities that it will rain in Lagos and Oyo on the same day are 43 and 21 respectively. Find the probability that it will not rain in both towns on the same day.
Worked solution (try it first)
It does not rain in Lagos with probability 1−43=41, and not in Oyo with probability 1−21=21.
No rain in either town means both of these happen, so multiply: 41×21=81, option B.